Fuel injected engines may be fed fuel under pressure by a fuel pump supplied from one or more fuel pickups in a fuel tank. “Returning fuel” systems have a pressure regulator located downstream of the fuel rail, for maintaining the pressure of fuel and for returning the uninjected fuel to the fuel tank. “Dead head” systems have a pressure regulator located upstream of the fuel injectors, for maintaining the fuel pressure and returning fuel pumped by the fuel pump but not sent to the fuel injectors. Off road vehicles, such as snowmobiles, personal watercraft, motorcycles, utility vehicles (for example, the Polaris Ranger), and all-terrain vehicles, have design challenges due to their intended use. Fuel tanks may often be tilted sideways, or front to back, as the vehicle traverses steep and/or bumpy terrain. Fuel is supplied to the fuel pump from a fuel pickup often disposed in the bottom of the fuel tank. When the fuel tank is partially empty and the fuel tank tilts, the fuel pickup may end up pulling in air and killing the engine, even though there is fuel at another location in the tank.
This has been addressed by adding a second fuel pickup elsewhere in the tank. This leaves the problem of one fuel pickup still sucking in air and causing the engine the sputter. This problem has been addressed by modifying the fuel pickups to close in the presence of air. This may prevent entry of some air, as the fuel pump pulls in fuel from a second pickup and none from the first, closed pickup. In some situations, both pickups may momentarily shut in the presence of air. In some situations, the fuel pump may pull a substantial vacuum, which keeps the fuel pickup in the closed position, even when the fuel pickup is once again covered with fuel. This can cause the engine to sputter or die.
In one example, in a half full fuel tank having two fuel pickups, one pickup may be exposed to air and closed for long periods. The other pickup may be exposed to fuel for long periods, and then exposed to air for a short period, as when a snowmobile goes downhill, exposing a rear, lower fuel pickup to air as the fuel shifts forward to cover the long closed, forward, upper fuel pickup. The fuel pump may pull a substantial vacuum against the front pickup, preventing it from opening, even in the presence of fuel. The engine can be starved for fuel, and miss and sputter, before being supplied fuel and recovering.
What would be desirable are systems to provide the engine with fuel even when the fuel tank is partially empty and the tank is tilted or bypassed.